RNA silencing of genes involved in Alzheimer's disease enhances mitochondrial function and synaptic activity

Gene therapy for CNS disorders: modalities, delivery and translational challenges

Gene therapy is emerging as a powerful tool to modulate abnormal gene expression, a hallmark of most CNS disorders. The transformative potentials of recently approved gene therapies for the treatment of spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS) and active cerebral adrenoleukodystrophy are encouraging further development of this approach. However, most attempts to translate gene therapy to the clinic have failed to make it to market. There is an urgent need not only to tailor the genes that are targeted to the pathology of interest but to also address delivery challenges and thereby maximize the utility of genetic tools. In this Review, we provide an overview of gene therapy modalities for CNS diseases, emphasizing the interconnectedness of different delivery strategies and routes of administration. Important gaps in understanding that could accelerate the clinical translatability of CNS genetic interventions are addressed, and we present lessons learned from failed clinical trials that may guide the future development of gene therapies for the treatment and management of CNS disorders.

Lipid nanoparticle mediated small interfering RNA delivery as a potential therapy for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative condition that exhibits a gradual decline in cognitive function and is prevalent among a significant number of individuals globally. The use of small interfering RNA (siRNA) molecules in RNA interference (RNAi) presents a promising therapeutic strategy for AD. Lipid nanoparticles (LNPs) have been developed as a delivery vehicle for siRNA, which can selectively suppress target genes, by enhancing cellular uptake and safeguarding siRNA from degradation. Numerous research studies have exhibited the effectiveness of LNP-mediated siRNA delivery in reducing amyloid beta (Aβ) levels and enhancing cognitive function in animal models of AD. The feasibility of employing LNP-mediated siRNA delivery as a therapeutic approach for AD is emphasized by the encouraging outcomes reported in clinical studies for other medical conditions. The use of LNP-mediated siRNA delivery has emerged as a promising strategy to slow down or even reverse the progression of AD by targeting the synthesis of tau phosphorylation and other genes linked to the condition. Improvement of the delivery mechanism and determination of the most suitable siRNA targets are crucial for the efficacious management of AD. This review focuses on the delivery of siRNA through LNPs as a promising therapeutic strategy for AD, based on the available literature.

Detrimental Roles of Hypoxia-Inducible Factor-1α in Severe Hypoxic Brain Diseases

Hypoxia stabilizes hypoxia-inducible factors (HIFs), facilitating adaptation to hypoxic conditions. Appropriate hypoxia is pivotal for neurovascular regeneration and immune cell mobilization. However, in central nervous system (CNS) injury, prolonged and severe hypoxia harms the brain by triggering neurovascular inflammation, oxidative stress, glial activation, vascular damage, mitochondrial dysfunction, and cell death. Diminished hypoxia in the brain improves cognitive function in individuals with CNS injuries. This review discusses the current evidence regarding the contribution of severe hypoxia to CNS injuries, with an emphasis on HIF-1α-mediated pathways. During severe hypoxia in the CNS, HIF-1α facilitates inflammasome formation, mitochondrial dysfunction, and cell death. This review presents the molecular mechanisms by which HIF-1α is involved in the pathogenesis of CNS injuries, such as stroke, traumatic brain injury, and Alzheimer's disease. Deciphering the molecular mechanisms of HIF-1α will contribute to the development of therapeutic strategies for severe hypoxic brain diseases.

VDAC1 Protein Regulation of Oxidative Damage and Mitochondrial Dysfunction-Mediated Cytotoxicity by Silica Nanoparticles in SH-SY5Y Cells

Silica nanoparticles (SiNPs) have been widely used in industry, electronics, and pharmaceutical industries. In addition, it is also widely used in medicine, tumor treatment and diagnosis, as well as other biomedical and biotechnology fields. The opportunities for people to contact SiNPs through iatrogenic, occupational, and environmental exposures are gradually increasing. The damage and biological effects of SiNPs on the nervous system have attracted widespread attention in the field of toxicology. Central nerve cells are rich in mitochondria. It is suggested that the effects of SiNPs on mitochondrial damage of nerve cells may involve the maintenance of neuronal membrane potential, the synthesis and operation of neurotransmitters, and the transmission of nerve pulses, and so on. We established an experimental model of SH-SY5Y cells to detect the cell survival rate, apoptosis, changes of reactive oxygen species and mitochondrial membrane potential, and the expression of mitochondrial function-related enzymes and proteins, so as to reveal the possible mechanism of SiNPs on neuronal mitochondrial damage. It was found that SiNPs could cause oxidative damage to cells and mitochondria, destroy some normal functions of mitochondria, and induce apoptosis in SH-SY5Y cells. The voltage-dependent anion channel 1(VDAC1) protein inhibitor DIDS could effectively reduce intracellular oxidative stress, such as the reduction of ROS content, and could also usefully restore some functional proteins of mitochondria to normal levels. The inhibition of VDAC1 protein may play an important role in the oxidative damage and dysfunction of neuronal mitochondria induced by SiNPs.

siRNA drug delivery across the blood-brain barrier in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease with a few FDA-approved drugs that provide modest symptomatic benefits and only two FDA-approved disease-modifying treatments for AD. The advancements in understanding the causative genes and non-coding sequences at the molecular level of the pathophysiology of AD have resulted in several exciting research papers that employed small interfering RNA (siRNA)-based therapy. Although siRNA is being sought by academia and biopharma industries, several challenges still need to be addressed. We comprehensively report the latest advances in AD pathophysiology, druggable targets, ongoing clinical trials, and the siRNA-based approaches across the blood-brain barrier for addressing AD. This review describes the latest delivery systems employed to address this barrier. Critical insights and future perspectives on siRNA therapy for AD are also provided.

Mitochondrial VDAC1: A Potential Therapeutic Target of Inflammation-Related Diseases and Clinical Opportunities

The multifunctional protein, voltage-dependent anion channel 1 (VDAC1), is located on the mitochondrial outer membrane. It is a pivotal protein that maintains mitochondrial function to power cellular bioactivities via energy generation. VDAC1 is involved in regulating energy production, mitochondrial oxidase stress, Ca²⁺ transportation, substance metabolism, apoptosis, mitochondrial autophagy (mitophagy), and many other functions. VDAC1 malfunction is associated with mitochondrial disorders that affect inflammatory responses, resulting in an up-regulation of the body’s defensive response to stress stimulation. Overresponses to inflammation may cause chronic diseases. Mitochondrial DNA (mtDNA) acts as a danger signal that can further trigger native immune system activities after its secretion. VDAC1 mediates the release of mtDNA into the cytoplasm to enhance cytokine levels by activating immune responses. VDAC1 regulates mitochondrial Ca²⁺ transportation, lipid metabolism and mitophagy, which are involved in inflammation-related disease pathogenesis. Many scientists have suggested approaches to deal with inflammation overresponse issues via specific targeting therapies. Due to the broad functionality of VDAC1, it may become a useful target for therapy in inflammation-related diseases. The mechanisms of VDAC1 and its role in inflammation require further exploration. We comprehensively and systematically summarized the role of VDAC1 in the inflammatory response, and hope that our research will lead to novel therapeutic strategies that target VDAC1 in order to treat inflammation-related disorders.

Transcriptomic and epigenomic landscapes of Alzheimer's disease evidence mitochondrial-related pathways

Alzheimers disease (AD) is the main cause of dementia and it is defined by cognitive decline coupled to extracellular deposit of amyloid-beta protein and intracellular hyperphosphorylation of tau protein. Historically, efforts to target such hallmarks have failed in numerous clinical trials. In addition to these hallmark-targeted approaches, several clinical trials focus on other AD pathological processes, such as inflammation, mitochondrial dysfunction, and oxidative stress. Mitochondria and mitochondrial-related mechanisms have become an attractive target for disease-modifying strategies, as mitochondrial dysfunction prior to clinical onset has been widely described in AD patients and AD animal models. Mitochondrial function relies on both the nuclear and mitochondrial genome. Findings from omics technologies have shed light on AD pathophysiology at different levels (e.g., epigenome, transcriptome and proteome). Most of these studies have focused on the nuclear-encoded components. The first part of this review provides an updated overview of the mechanisms that regulate mitochondrial gene expression and function. The second part of this review focuses on evidence of mitochondrial dysfunction in AD. We have focused on published findings and datasets that study AD. We analyzed published data and provide examples for mitochondrial-related pathways. These pathways are strikingly dysregulated in AD neurons and glia in sex-, cell- and disease stage-specific manners. Analysis of mitochondrial omics data highlights the involvement of mitochondria in AD, providing a rationale for further disease modeling and drug targeting.

Proteomic Analysis of Adult Human Hippocampal Subfields Demonstrates Regional Heterogeneity in the Protein Expression

Background: Distinct hippocampal subfields are known to get affected during aging, psychiatric disorders, and various neurological and neurodegenerative conditions. To understand the biological processes associated with each subfield, it is important to understand its heterogeneity at the molecular level. To address this lacuna, we investigated the proteomic analysis of hippocampal subfields─the cornu ammonis sectors (CA1, CA2, CA3, CA4) and dentate gyrus (DG) from healthy adult human cohorts. Findings: Microdissection of hippocampal subfields from archived formalin-fixed paraffin-embedded tissue sections followed by TMT-based multiplexed proteomic analysis resulted in the identification of 5,593 proteins. Out of these, 890 proteins were found to be differentially abundant among the subfields. Further bioinformatics analysis suggested proteins related to gene splicing, transportation, myelination, structural activity, and learning processes to be differentially abundant in DG, CA4, CA3, CA2, and CA1, respectively. A subset of proteins was selected for immunohistochemistry-based validation in an independent set of hippocampal samples. Conclusions: We believe that our findings will effectively pave the way for further analysis of the hippocampal subdivisions and provide awareness of its subfield-specific association to various neurofunctional anomalies in the future. The current mass spectrometry data is deposited and publicly made available through ProteomeXchange Consortium via the PRIDE partner repository with the data set identifier PXD029697.

Reduced VDAC1, Maintained Mitochondrial Dynamics and Enhanced Mitochondrial Biogenesis in a Transgenic Tau Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common forms of neurodegeneration, defined by reduced cognitive function, which is caused by the gradual death of neurons in the brain. Recent studies have shown an age-dependent rise in the levels of voltage-dependent anion channel 1 (VDAC1) in AD. In addition, we discovered an aberrant interaction between VDAC1 and P-TAU in the brains of AD patients, which led to abnormalities in the structural and functional integrity of the mitochondria. The purpose of our study is to understand the protective effects of reduced VDAC1 against impaired mitochondrial dynamics and defective mitochondrial biogenesis in transgenic TAU mice. Recently, we crossed heterozygote VDAC1 knockout (VDAC1+/-) mice with transgenic TAU mice to obtain double-mutant VDAC1+/-/TAU mice. Our goal was to evaluate whether a partial decrease in VDAC1 lessens the amount of mitochondrial toxicity in transgenic Tau (P301L) mice. We found that mitochondrial fission proteins were significantly reduced, and mitochondrial fusion and biogenesis proteins were increased in double-mutant mice compared to TAU mice. On the basis of these discoveries, the current work may have significance for the development of reduced-VDAC1-based treatments for individuals suffering from AD as well as other tauopathies.

A partial reduction of VDAC1 enhances mitophagy, autophagy, synaptic activities in a transgenic Tau mouse model

Alzheimer's disease (AD) is the most common cause of mental dementia in the aged population. AD is characterized by the progressive decline of memory and multiple cognitive functions, and changes in behavior and personality. Recent research has revealed age-dependent increased levels of VDAC1 in postmortem AD brains and cerebral cortices of APP, APPxPS1, and 3xAD.Tg mice. Further, we found abnormal interaction between VDAC1 and P-Tau in the AD brains, leading to mitochondrial structural and functional defects. Our current study aimed to understand the impact of a partial reduction of voltage-dependent anion channel 1 (VDAC1) protein on mitophagy/autophagy, mitochondrial and synaptic activities, and behavior changes in transgenic TAU mice in Alzheimer's disease. To determine if a partial reduction of VDAC1 reduces mitochondrial and synaptic toxicities in transgenic Tau (P301L) mice, we crossed heterozygote VDAC1 knockout (VDAC1^+/- ) mice with TAU mice and generated double mutant (VDAC1^+/- /TAU) mice. We assessed phenotypic behavior, protein levels of mitophagy, autophagy, synaptic, other key proteins, mitochondrial morphology, and dendritic spines in TAU mice relative to double mutant mice. Partial reduction of VDAC1 rescued the TAU-induced behavioral impairments such as motor coordination and exploratory behavioral changes, and learning and spatial memory impairments in VDAC1^+/- /TAU mice. Protein levels of mitophagy, autophagy, and synaptic proteins were significantly increased in double mutant mice compared with TAU mice. In addition, dendritic spines were significantly increased; the mitochondrial number was significantly reduced, and mitochondrial length was increased in double mutant mice. Based on these observations, we conclude that reduced VDAC1 is beneficial in symptomatic-transgenic TAU mice.

Rapamycin Attenuated Zinc-Induced Tau Phosphorylation and Oxidative Stress in Rats: Involvement of Dual mTOR/p70S6K and Nrf2/HO-1 Pathways

Alzheimer’s disease is pathologically characterized by abnormal accumulation of amyloid-beta plaques, neurofibrillary tangles, oxidative stress, neuroinflammation, and neurodegeneration. Metal dysregulation, including excessive zinc released by presynaptic neurons, plays an important role in tau pathology and oxidase activation. The activities of mammalian target of rapamycin (mTOR)/ribosomal S6 protein kinase (p70S6K) are elevated in the brains of patients with Alzheimer’s disease. Zinc induces tau hyperphosphorylation via mTOR/P70S6K activation in vitro. However, the involvement of the mTOR/P70S6K pathway in zinc-induced oxidative stress, tau degeneration, and synaptic and cognitive impairment has not been fully elucidated in vivo. Here, we assessed the effect of pathological zinc concentrations in SH-SY5Y cells by using biochemical assays and immunofluorescence staining. Rats (n = 18, male) were laterally ventricularly injected with zinc, treated with rapamycin (intraperitoneal injection) for 1 week, and assessed using the Morris water maze. Evaluation of oxidative stress, tau phosphorylation, and synaptic impairment was performed using the hippocampal tissue of the rats by biochemical assays and immunofluorescence staining. The results from the Morris water maze showed that the capacity of spatial memory was impaired in zinc-treated rats. Zinc sulfate significantly increased the levels of P-mTOR Ser2448, P-p70S6K Thr389, and P-tau Ser356 and decreased the levels of nuclear factor erythroid 2-related factor-2 (Nrf2) and heme oxygenase-1 (HO-1) in SH-SY5Y cells and in zinc-treated rats compared with the control groups. Increased expression of reactive oxygen species was observed in zinc sulfate-induced SH-SY5Y cells and in the hippocampus of zinc-injected rats. Rapamycin, an inhibitor of mTOR, rescued zinc-induced increases in mTOR/p70S6K activation, tau phosphorylation, and oxidative stress, and Nrf2/HO-1 inactivation, cognitive impairment, and synaptic impairment reduced the expression of synapse-related proteins in zinc-injected rats. In conclusion, our findings imply that rapamycin prevents zinc-induced cognitive impairment and protects neurons from tau pathology, oxidative stress, and synaptic impairment by decreasing mTOR/p70S6K hyperactivity and increasing Nrf2/HO-1 activity.

Exosomes in Alzheimer's Disease: From Being Pathological Players to Potential Diagnostics and Therapeutics

Exosomes (EXOs) were given attention as an extracellular vesicle (EV) with a pivotal pathophysiological role in the development of certain neurodegenerative disorders (NDD), such as Parkinson's and Alzheimer's disease (AD). EXOs have shown the potential to carry pathological and therapeutic cargo; thus, researchers have harnessed EXOs in drug delivery applications. EXOs have shown low immunogenicity as natural drug delivery vehicles, thus ensuring efficient drug delivery without causing significant adverse reactions. Recently, EXOs provided potential drug delivery opportunities in AD and promising future clinical applications with the diagnosis of NDD and were studied for their usefulness in disease detection and prediction prior to the emergence of symptoms. In the future, the microfluidics technique will play an essential role in isolating and detecting EXOs to diagnose AD before the development of advanced symptoms. This review is not reiterative literature but will discuss why EXOs have strong potential in treating AD and how they can be used as a tool to predict and diagnose this disorder.

Regulation of PPARα by APP in Alzheimer disease affects the pharmacological modulation of synaptic activity

Among genetic susceptibility loci associated with late-onset Alzheimer disease (LOAD), genetic polymorphisms identified in genes encoding lipid carriers led to the hypothesis that a disruption of lipid metabolism could promote disease progression. We previously reported that amyloid precursor protein (APP) involved in Alzheimer disease (AD) physiopathology impairs lipid synthesis needed for cortical networks' activity and that activation of peroxisome proliferator-activated receptor α (PPARα), a metabolic regulator involved in lipid metabolism, improves synaptic plasticity in an AD mouse model. These observations led us to investigate a possible correlation between PPARα function and full-length APP expression. Here, we report that PPARα expression and activation were inversely related to APP expression both in LOAD brains and in early-onset AD cases with a duplication of the APP gene, but not in control human brains. Moreover, human APP expression decreased PPARA expression and its related target genes in transgenic mice and in cultured cortical cells, while opposite results were observed in APP-silenced cortical networks. In cultured neurons, APP-mediated decrease or increase in synaptic activity was corrected by a PPARα-specific agonist and antagonist, respectively. APP-mediated control of synaptic activity was abolished following PPARα deficiency, indicating a key function of PPARα in this process.

Autophagy as a Target for the Retinoprotective Effects of the Mitochondria-Targeted Antioxidant SkQ1

Age-related macular degeneration (AMD) is a complex neurodegenerative disease, a main cause of vision loss in elderly people. The pathogenesis of dry AMD, the most common form of AMD (~ 80% cases), involves degenerative changes in the retinal pigment epithelium (RPE), which are closely associated with the age-associated impairments in autophagy. Reversion of these degenerative changes is considered as a promising approach for the treatment of this incurable disease. The purpose of our study was to assess the relationship between previously identified retinoprotective effects of the mitochondrial antioxidant plastoquinonyl-decyl-triphenylphosphonium (SkQ1) and its influence on the autophagy process in senescence-accelerated OXYS rats characterized by the development of AMD-like retinopathy (Wistar rats were used as a control). The treatment with SkQ1 (250 nmol/kg body weight) during the period of active disease progression (from 12 to 18 months of age) completely prevented progression of clinical manifestations of retinopathy in the OXYS rats, suppressed atrophic changes in the RPE cells and activated autophagy in the retina, which was evidenced by a significant decrease in the content of the multifunctional adapter protein p62/Sqstm1 and increase in the level of the Beclin1 gene mRNA. In general, the results obtained earlier and in the present study have shown that SkQ1 is a promising agent for prevention and suppression of AMD.

siRNA Therapeutics: Future Promise for Neurodegenerative Diseases

Neurodegenerative diseases (ND), as a group of central nervous system (CNS) disorders, are among the most prominent medical problems of the 21st century. They are often associated with considerable disability, motor dysfunction and dementia and are more common in the aged population. ND imposes a psychologic, economic and social burden on the patients and their families. Currently, there is no effective treatment for ND. Since many ND result from the gain of function of a mutant allele, small interference RNA (siRNA) can be a potential therapeutic agent for ND management. Based on the RNA interference (RNAi) approach, siRNA is a powerful tool for modulating gene expression through gene silencing. However, there are some obstacles in the clinical application of siRNA, including unfavorable immune response, off-target effects, instability of naked siRNA, nuclease susceptibility and a need to develop a suitable delivery system. Since there are some issues related to siRNA delivery routes, in this review, we focus on the application of siRNA in the management of ND treatment from 2000 to 2020.

Exploring genetic variants in obsessive compulsive disorder severity: A GWAS approach

BACKGROUND

The severity of Obsessive-Compulsive Disorder (OCD) varies significantly among probands. No study has specifically investigated the genetic base of OCD severity. A previous study from our group found an OCD polygenic risk score to predict pre- and post-treatment severity. This study explores the genomic bases of OCD severity.

METHODS

We administered the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) to 401 patients at their first visit to our clinic to measure their OCD severity. Genotyping data was collected by using the Infinium PsychArray-24 BeadChip kit (Illumina). We analyzed genetic association with OCD severity in a linear regression analysis at single-nucleotide polymorphism (SNP)- and gene-levels, this last also considering rare variants. Enrichment analyses were performed from gene-based analyses' results.

RESULTS

No SNP reached significant association (p < 10^-8) with the YBOCS. Six markers showed suggestive association (p < 10^-5). The top SNP was an intergenic variant in chromosome 2: rs7578149 (p < 1.89 × 10^-6), located in a region suggestively associated with MDD. Linkage disequilibrium was found for two clusters of SNPs located between SLC16A14 and SP110 in chromosome 2, all of them forming one peak of association. Enrichment analyses revealed OCD genes to be associated with porin activity (FDR = 0.01) and transmembrane structure (FDR = 0.04).

LIMITATIONS

The size of the sample and the transversal nature of the severity measure are limitations of this study.

CONCLUSION

This study contributes to better characterize OCD at an individual level, helping to know more about the prognosis of the disorder and develop more individualized treatments.

The Evolution of Tau Phosphorylation and Interactions

Tau is a neuronal microtubule-associated protein (MAP) that is involved in the regulation of axonal microtubule assembly. However, as a protein with intrinsically disordered regions (IDRs), tau also interacts with many other partners in addition to microtubules. Phosphorylation at selected sites modulates tau's various intracellular interactions and regulates the properties of IDRs. In Alzheimer's disease (AD) and other tauopathies, tau exhibits pathologically increased phosphorylation (hyperphosphorylation) at selected sites and aggregates into neurofibrillary tangles (NFTs). By bioinformatics means, we tested the hypothesis that the sequence of tau has changed during the vertebrate evolution in a way that novel interactions developed and also the phosphorylation pattern was affected, which made tau prone to the development of tauopathies. We report that distinct regions of tau show functional specialization in their molecular interactions. We found that tau's amino-terminal region, which is involved in biological processes related to "membrane organization" and "regulation of apoptosis," exhibited a strong evolutionary increase in protein disorder providing the basis for the development of novel interactions. We observed that the predicted phosphorylation sites have changed during evolution in a region-specific manner, and in some cases the overall number of phosphorylation sites increased owing to the formation of clusters of phosphorylatable residues. In contrast, disease-specific hyperphosphorylated sites remained highly conserved. The data indicate that novel, non-microtubule related tau interactions developed during evolution and suggest that the biological processes, which are mediated by these interactions, are of pathological relevance. Furthermore, the data indicate that predicted phosphorylation sites in some regions of tau, including a cluster of phosphorylatable residues in the alternatively spliced exon 2, have changed during evolution. In view of the "antagonistic pleiotropy hypothesis" it may be worth to take disease-associated phosphosites with low evolutionary conservation as relevant biomarkers into consideration.

Hypoxia and Inflammation as a Consequence of β-Fibril Accumulation: A Perspective View for New Potential Therapeutic Targets

Amyloidoses are heterogeneous diseases that result from the deposition of toxic insoluble β-sheet fibrillar protein aggregates in different tissues. The cascade of molecular events leading to amyloidoses and to the related clinical manifestations is not completely understood. Nevertheless, it is known that tissue damage associated to this disease involves alteration of tissue architecture, interaction with cell surface receptors, inflammation elicited by the amyloid protein deposition, oxidative stress, and apoptosis. However, another important aspect to consider is that systemic protein massive deposition not only subverts tissue architecture but also determines a progressive cellular hypertrophy and dilation of the extracellular space enlarging the volume of the organ. Such an alteration increases the distance between cells and vessels with a drop in pO₂ that, in turn, causes both necrotic cell death and activation of the hypoxia transcription factor HIF-1α. Herewith, we propose the hypothesis that both cell death and hypoxia represent two important events for the pathogenesis of damage and progression of amyloidoses. In fact, molecules released by necrotic cells activate inflammatory cells from one side while binding to HIF-1α-dependent membrane receptors expressed on hypoxic parenchymal cells on the other side. This latter event generates a signaling cascade triggering NFκB activation and chronic inflammation. Finally, we also suggest that this scenario, once proved and detailed, might suggest important targets for new therapeutic interventions.

Early Life Stress and Epigenetics in Late-onset Alzheimer's Dementia: A Systematic Review

Involvement of life stress in Late-Onset Alzheimer's Disease (LOAD) has been evinced in longitudinal cohort epidemiological studies, and endocrinologic evidence suggests involvements of catecholamine and corticosteroid systems in LOAD. Early Life Stress (ELS) rodent models have successfully demonstrated sequelae of maternal separation resulting in LOAD-analogous pathology, thereby supporting a role of insulin receptor signalling pertaining to GSK-3beta facilitated tau hyper-phosphorylation and amyloidogenic processing. Discussed are relevant ELS studies, and findings from three mitogen-activated protein kinase pathways (JNK/SAPK pathway, ERK pathway, p38/MAPK pathway) relevant for mediating environmental stresses. Further considered were the roles of autophagy impairment, neuroinflammation, and brain insulin resistance. For the meta-analytic evaluation, 224 candidate gene loci were extracted from reviews of animal studies of LOAD pathophysiological mechanisms, of which 60 had no positive results in human LOAD association studies. These loci were combined with 89 gene loci confirmed as LOAD risk genes in previous GWAS and WES. Of the 313 risk gene loci evaluated, there were 35 human reports on epigenomic modifications in terms of methylation or histone acetylation. 64 microRNA gene regulation mechanisms were published for the compiled loci. Genomic association studies support close relations of both noradrenergic and glucocorticoid systems with LOAD. For HPA involvement, a CRHR1 haplotype with MAPT was described, but further association of only HSD11B1 with LOAD found; however, association of FKBP1 and NC3R1 polymorphisms was documented in support of stress influence to LOAD. In the brain insulin system, IGF2R, INSR, INSRR, and plasticity regulator ARC, were associated with LOAD. Pertaining to compromised myelin stability in LOAD, relevant associations were found for BIN1, RELN, SORL1, SORCS1, CNP, MAG, and MOG. Regarding epigenetic modifications, both methylation variability and de-acetylation were reported for LOAD. The majority of up-to-date epigenomic findings include reported modifications in the well-known LOAD core pathology loci MAPT, BACE1, APP (with FOS, EGR1), PSEN1, PSEN2, and highlight a central role of BDNF. Pertaining to ELS, relevant loci are FKBP5, EGR1, GSK3B; critical roles of inflammation are indicated by CRP, TNFA, NFKB1 modifications; for cholesterol biosynthesis, DHCR24; for myelin stability BIN1, SORL1, CNP; pertaining to (epi)genetic mechanisms, hTERT, MBD2, DNMT1, MTHFR2. Findings on gene regulation were accumulated for BACE1, MAPK signalling, TLR4, BDNF, insulin signalling, with most reports for miR-132 and miR-27. Unclear in epigenomic studies remains the role of noradrenergic signalling, previously demonstrated by neuropathological findings of childhood nucleus caeruleus degeneration for LOAD tauopathy.

Maternal imprinting on cognition markers of wild type and transgenic Alzheimer's disease model mice

The risk of suffering from Alzheimer’s disease (AD) is higher in individuals from AD-affected mothers. The purpose of this investigation was to study whether maternal transmission might produce AD-related alterations in progenies of mice that do not have any genotypic alteration. We used cognitively-intact mothers harbouring in heterozygosity the transgene for overexpressing the Swedish double mutant version of the human amyloid precursor protein (hAβPPswe). The phenotype of the offspring with or without the transgene resulting from crossing young Tg2576 females with wild-type males were compared with those of the offspring resulting from crossing wild-type females with Tg2576 males. The hAβPPswe-bearing offspring from Tg2576 mothers showed an aggravated AD-like phenotype. Remarkably, cognitive, immunohistochemical and some biochemical features displayed by Tg2576 heterozygous mice were also found in wild-type animals generated from Tg2576 females. This suggests the existence of a maternal imprinting in the wild-type offspring that confers a greater facility to launch an AD-like neurodegenerative cascade. Such progeny, lacking any mutant amyloid precursor protein, constitutes a novel model to study maternal transmission of AD and, even more important, to discover early risk markers that predispose to the development of AD.

Have there been improvements in Alzheimer's disease drug discovery over the past 5 years?

INTRODUCTION

Alzheimer's disease (AD) is the most important neurodegenerative disorder with a global cost worldwide of over $700 billion. Pharmacological treatment accounts for 10-20% of direct costs; no new drugs have been approved during the past 15 years; and the available medications are not cost-effective. Areas covered: A massive scrutiny of AD-related PubMed publications (ps)(2013-2017) identified 42,053ps of which 8,380 (19.60%) were associated with AD treatments. The most prevalent pharmacological categories included neurotransmitter enhancers (11.38%), multi-target drugs (2.45%), anti-Amyloid agents (13.30%), anti-Tau agents (2.03%), natural products and derivatives (25.58%), novel drugs (8.13%), novel targets (5.66%), other (old) drugs (11.77%), anti-inflammatory drugs (1.20%), neuroprotective peptides (1.25%), stem cell therapy (1.85%), nanocarriers/nanotherapeutics (1.52%), and others (<1% each). Expert opinion: Unsuccessful outcomes in AD therapeutics are attributed to pathogenic misconceptions, erratic procedures in drug development and inappropriate regulations. Recommendations for the future are as follows: (i) the reconsideration of dominant pathogenic theories, (ii) the identification of reliable biomarkers, (iii) the redefinition of diagnostic criteria, (iv) new guidelines for disease management, (v) the reorientation of drug discovery programs, (vi) the updating of regulatory requirements, (vii) the introduction of pharmacogenomics in drug development and personalized treatments, and (viii) the implementation of preventive programs.

Mitochondrial VDAC1: A Key Gatekeeper as Potential Therapeutic Target

Mitochondria are the key source of ATP that fuels cellular functions, and they are also central in cellular signaling, cell division and apoptosis. Dysfunction of mitochondria has been implicated in a wide range of diseases, including neurodegenerative and cardiac diseases, and various types of cancer. One of the key proteins that regulate mitochondrial function is the voltage-dependent anion channel 1 (VDAC1), the most abundant protein on the outer membrane of mitochondria. VDAC1 is the gatekeeper for the passages of metabolites, nucleotides, and ions; it plays a crucial role in regulating apoptosis due to its interaction with apoptotic and anti-apoptotic proteins, namely members of the Bcl-2 family of proteins and hexokinase. Therefore, regulation of VDAC1 is crucial not only for metabolic functions of mitochondria, but also for cell survival. In fact, multiple lines of evidence have confirmed the involvement of VDAC1 in several diseases. Consequently, modulation or dysregulation of VDAC1 function can potentially attenuate or exacerbate pathophysiological conditions. Understanding the role of VDAC1 in health and disease could lead to selective protection of cells in different tissues and diverse diseases. The purpose of this review is to discuss the role of VDAC1 in the pathogenesis of diseases and as a potentially effective target for therapeutic management of various pathologies.

Prospects of siRNA applications in regenerative medicine

Small interfering RNA (siRNA) has established its reputation in the field of tissue engineering owing to its ability to silence the proteins that inhibit tissue regeneration. siRNA is capable of regulating cellular behavior during tissue regeneration processes. The concept of using siRNA technology in regenerative medicine derived from its ability to inhibit the expression of target genes involved in defective tissues and the possibility to induce the expression of tissue-inductive factors that improve the tissue regeneration process. To date, siRNA has been used as a suppressive biomolecule in different tissues, such as nervous tissue, bone, cartilage, heart, kidney, and liver. Moreover, various delivery systems have been applied in order to deliver siRNA to the target tissues. This review will provide an in-depth discussion on the development of siRNA and their delivery systems and mechanisms of action in different tissues.

A disease with a sweet tooth: exploring the Warburg effect in Alzheimer's disease

After more than 80 years from the revolutionary discoveries of Otto Warburg, who observed high glucose dependency, with increased glycolysis and lactate production regardless of oxygen availability in most cancer cells, the 'Warburg effect' returns to the fore in neuronal cells affected by Alzheimer's disease (AD). Indeed, it seems that, in the mild phase of AD, neuronal cells "prefer" to use the energetically inefficient method of burning glucose by glycolysis, as in cancer, proving to become resistant to β-amyloid (Aβ)-dependent apoptosis. However, in the late phase, while most AD brain cells die in response to Aβ toxicity, only small populations of neurons, exhibiting increased glucose uptake and glycolytic flux, are able to survive as they are resistant to Aβ. Here we draw an overview on the metabolic shift for glucose utilization from oxidative phosphorylation to glycolysis, focusing on the hypothesis that, as extreme attempt to oppose the impending death, mitochondria-whose dysfunction and central role in Aβ toxicity is an AD hallmark-are sent into quiescence, this likely contributing to activate mechanisms of resistance to Aβ-dependent apoptosis. Finally, the attempt turns out fruitless since the loss of the adaptive advantage afforded by elevated aerobic glycolysis exacerbates the pathophysiological processes associated with AD, making the brain susceptible to Aβ-induced neurotoxicity and leading to cell death and dementia. The understanding of how certain nerve cells become resistant to Aβ toxicity, while the majority dies, is an attractive challenge toward the identification of novel possible targets for AD therapy.

Levels of 17β-Hydroxysteroid Dehydrogenase Type 10 in Cerebrospinal Fluid of People with Mild Cognitive Impairment and Various Types of Dementias

BACKGROUND

Overexpression of the mitochondrial enzyme 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10, which is also known as the intracellular amyloid-β peptide (Aβ) binding protein) is observed in cortical or hippocampal regions of patients with Alzheimer's disease (AD). It appears that 17β-HSD10 may play a role in the pathogenesis of AD.

OBJECTIVE

We investigated the possibility that levels of 17β-HSD10 in cerebrospinal fluid could be a prospective biomarker of AD.

METHODS

We estimated the enzyme levels in 161 people (15 non-demented controls, 52 people with mild cognitive impairment (MCI), 35 people with probable AD, or 59 people with other types of dementia) and compared them with those of Aβ(1- 42), tau, and phospho-tau.

RESULTS

We found significantly higher levels of 17β-HSD10 in people with MCI due to AD (to 109.9% ), with AD (to 120.0% ), or with other types of dementia (to 110.9% ) when compared to the control group. The sensitivity of the new biomarker to AD was 80.0% , and the specificity was 73.3% (compared to controls) or 52.5-59.1% (compared to other types of dementia). Results of multiple linear regression and of correlation analysis revealed AD-mediated changes in links between 17β-HSD10 and Mini Mental State Examination score.

CONCLUSION

It seems that changes in 17β-HSD10 start many years before symptom onset, analogous to those in Aβ1 - 42, tau, or phospho-tau and that the levels are a relatively highly sensitive but unfortunately less specific biomarker of AD. A role of 17β-HSD10 overexpression in AD is discussed.

Multiple faces of dynamin-related protein 1 and its role in Alzheimer's disease pathogenesis

Mitochondria play a large role in neuronal function by constantly providing energy, particularly at synapses. Recent studies suggest that amyloid beta (Aβ) and phosphorylated tau interact with the mitochondrial fission protein, dynamin-related protein 1 (Drp1), causing excessive fragmentation of mitochondria and leading to abnormal mitochondrial dynamics and synaptic degeneration in Alzheimer's disease (AD) neurons. Recent research also revealed Aβ-induced and phosphorylated tau-induced changes in mitochondria, particularly affecting mitochondrial shape, size, distribution and axonal transport in AD neurons. These changes affect mitochondrial health and, in turn, could affect synaptic function and neuronal damage and ultimately leading to memory loss and cognitive impairment in patients with AD. This article highlights recent findings in the role of Drp1 in AD pathogenesis. This article also highlights Drp1 and its relationships to glycogen synthase kinase 3, cyclin-dependent kinase 5, p53, and microRNAs in AD pathogenesis.